Bergstrom-Boyce is a special hyperviscoelasticity material model intended specifically for elastomer materials.
To add this material model to your analysis, right-click the Bergstrom-Boyce option contained in the Hyperviscoelasticity category of the Toolbox and select . You can also add the material by double-clicking the option.
Limitation: Note that this material model does not support the Engineering Data option . As a result, the material properties are not affected when you change the units in the Workbench Unit drop-down menu. You must manually change the units for the material using the Stress Units and Time Units properties of the material.
For the theoretical background of this material model, the steps to use it, as well as a description of the generated output, see the Bergstrom-Boyce Material topic in the Special Hyperelasticity section of the Mechanical APDL Material Reference.